Preventing user errors by systematic analysis of deviations from the system task model

Interactive safety-critical applications have specific requirements that cannot be completely captured by traditional evaluation techniques. In this paper, we discuss how to perform a systematic inspection-based analysis to improve both usability and safety aspects of an application. The analysis considers a system prototype and the related task model and aims to evaluate what could happen when interactions and behaviours occur differently from what the system design assumes. We also provide a description and discussion of an application of this method to a case study in the air traffic control domain. # 2002 Elsevier Science Ltd.